Certain cyclopentanone derivatives are already known in the art of perfumery and in that of flavours. Some of them represent very valuable materials whose utility in the field is well established. Jasmone, methyl jasmonate and methyl dihydrojasmonate for instance [see S. Arctander, Perfume and Flavor Chemicals, Montclair N.J. (1969) USA; Sect. 1788, 2093 and 2076, respectively], are known to possess floral, jasmin-like odoriferous notes of great elegance. Analogous properties are shown by 2-n-hexyl- and 2-n-pentyl-cyclopentanone [S. Arctander, op. cit.; Sect. 1659 and 1534, respectively], whereas scientific literature reports that 2,2,5-trimethyl-cyclopentanone, 2,2,5,5-tetramethyl-cyclopentanone and 2-methyl-2,5,5-tripropyl-cyclopentanone possess weak odours of minty, camphery and anise type of no recognized utility for the art.